Apparatus for precasting concrete stair structures



F. KOGL May 5, 1942.

APPARATUS FOR PRECASTING CONCRETE STAIR STRUCTURES 4 SheetsSheet 1 Filed July 31, 1939 May 5, 1942. F. KOGL 2,281,6 98

APPARATUS FOR PRECASTING CONCRETE STAIR STRUCTURES Filed July 31,1939 4 Sheets-Sheet 2 -/az x T #3 m0 xvz 0 o w 2,] Wu e/wbcyo FE M/K Kazan Cit $414K May 5, 1942. v v KOGL 2,281,698

APPARATUS FOR PRECASTING CONCRETE STAIR STRUCTURES Filed July 31, 1939 4 Shgets$heet 3 w as Q i W j g rvuc/wbom FIeANK 4 004 May 5, 1942. KQGL, 2,281,698

APPARATUS FOR PRECASTING CONCRETE STAIRSTRUCTURES Filed July 31, 1939 4 Sheets-Sheet 4 A'eA/vk K061.

Patented May 5, 1942 APPARATUS FOR PRECASTING CONCRETE STAIR- STRUCTURES Frank Kogl, St. Paul, Minn., assignor of two and one-half per cent to Walter H. Carlson, two and one-half per cent to Ora E. Carlson, four per cent to Minnie C. Schneider, four per cent to Genevieve Clark, and ten per cent to Ruby S. McBride, all of St. Paul, Minn. Application July 31, 1939, Serial No. 287,513

Claims.

This invention relates to an apparatus for precasting concrete stair structures.

The primary object of the invention is to provide an apparatus in the form of a sectional mold assembly by the use of which concrete stairs or steps of the type used for building entrances and lawn terraces may be rapidly and inexpensively precast in a single light and extremely durable monolithic unit. Another object is to provide an apparatus of this kind which is readily set up and adjusted for casting a step structure of almost any desired width and height and with any number of steps. A further object is to provide an apparatus for this purpose which may be rapidly and readily set up to receive the cementitious mixture and then, when said mixture has solidified and hardened sufficiently, may be rapidly dismantled as necessary to remove it from the finished cast structure. A further object is to provide an apparatus by which the castmg operation may be carried out in a manner to so form the finished and exposed surfaces of the cast structure that no subsequent or supplementary finishing and touching operations will be necessary.

These and other more detailed and specific objects will be disclosed in the course of the following specification, reference being had to the accompanying drawings, in which- Fig. 1 is a side view of my improved apparatus, portions being broken away and shown in section to disclose interior construction, and the end extension mold being shown as separated slightly from the main mold.

Fig. 2 is an enlarged vertical cross sectional view through a fragmental portion of the mold and showing the removable plug member for forming post sockets in the finished structure.

Fig. 3 is an enlarged inverted plan view of a corner portion of the mold showing the jack screw assembly for separating inner and outer forms.

Fig. 4 is a plan view of the main mold structure with a large part broken away to show a power lift assembly for separating the inner mold from the completed cast structure.

Fig. 5 is a perspective view of the completed cast structure as formed by use of my apparatus.

Fig. 6 is an enlarged fragmentary vertical section along the line 6-6 in Fig. 4.

Fig. 7 is a longitudinal vertical section through the complete mold assembly showing the same as inverted and partially filled with the cementitious mixture and showing a framework for properly supporting the assembly in this position.

Fig. 8 is an enlarged sectional detail view showing a modified form of clip device for fastening sections of the mold together. i

Fig. an an enlarged vertical section along the line 9-4 in Fig. 1.

Fig. 10 is a rear end view of the completed cast structure.

Referring now with more particularity and by reference characters to the drawings, my improved apparatus or mold is shown generally at A and comprises as its basic elements an outer form B and inner form C. These forms are assembled, in the set up condition of the mold shown in Figs. 1, 4, and 7, to provide intervening cavities and recesses into which the cementitious mixture may be poured and allowed to harden to provide a step structure as shown in Fig. 5. This structure comprises a series (here shown as three in number) of steps each having a tread D and riser E, and which are bounded laterally by the panelled sides or side walls F and the forwardly sloping side runners G; The wall thickness at all points may be of any desired dimension, but it is of course to be understood that the entire underside of the structure is hollow in order to reduce weight and effect a saving in material. The uppermost, or rear, step tread D may be extended rearwardly to form a platform or small stoop H where desired, and this is accomplished by the use of an extension mold shown generally at A and made up of outer and inner forms B and C as will hereinafter appear.

In whatever length selected the rear end. of the structure has an arched rear wall I (shown in Fig. 10) cut away centrally as shown and panelled as indicated at J so that only a narrow, outer rim or band K is left projecting. This facilitates the butting of the steps up against a rough stone wall since only a narrow, inverted U-shaped section of stone must be faced off to properly fit the band K as will be readily evident.

Turning now to details of construction, the outer form B comprises side members I adapted to stand on edge vertically and having inwardly turned and forwardly sloping runner forming top members P2. The side members are recessed or pressed inwardly as shown at l3, to form an inset panelled surface for the sides F and vertical rib portions 14 are formed in this inset panel to form reinforcing ribs or buttresses L on the sides F. The inner margins of the top members I2 are provided with angle iron connecting strips I 6 having webs set on edge vertically to meet mounting strips ['1 extended vertically from the end or cheek portions 18 of the riser and tread plate l 9. Said plate I9 is formed with alternately vertical and horizontal riser and tread forming portions and 2|, respectively, and at its ends meets at 23 with the said top members I2.

The strips It and I! are detachably joined "by any suitable fasteners to complete the outer form and hold the several parts thereof in position. It is desirable, however, that these fasteners be of a kind which may be quickly put in .place or removed in order to facilitate setting up and taking down the mold, and for this purpose I may employ clips or clip fasteners such as shown generally at 24 throughout the drawings. These fasteners each comprises a yoke 25 having a tapped socket 225 at one end 'toreceive' a screw 27, the end of which is adapted to enter registering apertures 28 in the strips [6 and H. The other end of the yoke is forked at 29 to bear against either of the strips clear of the screw end while the screw has a collar 30 to bear against the other strip and so-urge the parts together. By the use of a socket wrench (not shown) on the faced end of the screw it willbe apparent that this fastener may be quickly applied or removed.

inafter-appear, for connecting the extension mold A.

The inner form C-likewise comprises side members 33 which set on edge vertically within the outer form sides -I I andwhich have the integrally formed-inner top or runner forming members 345 and downwardly turned inner cheek'portions 3-5 which stand in spaced relation to the corresponding portions 1 2 and t8 of the outer form. The inner riserformin'g plates 36 are butted at 31 to 'theend's of thecheek members and are removably connected thereto by angle iron strips 38 secured to the ends of the plates and meeting strips .38 secured to the lower-edges of the cheek members asshown. Fasteners such as 24 may be employed in making these connections or slotted :pins '40 may be inserted through holes t! in the strips and retained by wedges 42a in the manner clearly shown.

The plates 36 are an integral part of the inner riserand tread forming member 42, but the portions thereof forming the inner sides of the treads are cut out to leave only marginal frames 3. The openings thus formed are covered by removable inner tread plates 44 which are retained in place by long bolts 45 hooked at their headed ends in forks 46 secured 'on the frames '43 and having wing nuts '47 to engage similar and aligned forks 48 at the opposite sides of the frames. The bolts thus traverse the inner-tread plates 44 and it will be noted'that the bolt heads 49 and the loose collars 5i! on the bolts are so shaped, as wellas the forks 45 and "at, that the bolts will move toward the plates as the wing nuts are drawn tightgand so will urge the plates tightlyragainst the frames The margins of the plates 44 may be turned downwardly all arcundras shown at 5| to stiffen the plates.

The lower margins of the inner form C are braced "by angle flirions 52 and suitable bracing between the side members 33 and cheek members 35 maybe arranged as shown at 53.

The inner form C is s'et'within the outer form B and is held imposition by tie bars or cross bars 54 "which are secured to the angle Lirons 3! by bolts 55 and to angle iron 52 by slotted :pins and wedges shown generally at 56. The forms are thus held rigidly in spaced relation defining intervening recesses or cavities into which the cernentitious mixture may be poured to form the step sides F, and the risers and treads E and D, as will be apparent.

The outer tread forming plates it may be corrugated or formed with bosses (as at I25 in Fig. 9-) to form non-skid means on the treads.

The outer form'B' of the extension mold A comprises side members 5! turned inwardly at their upper ends at -58 to meet an outer platform forming plate 59, the adjacent or meeting margins of :thes'ejparts carrying angle iron connecting strips B0 and 6! which may be secured -togetherby fasteners such as 2d. The side members '57 are inset at 62 to form panels in the extended sides of the completed cast structure,

The "inner extension form C comprises side members 61 which at their upper ends are connected by angle irons 63 to an inner platform plate frame member 69 in the manner hereinbefore set forth. The opening through this frame mem'ber-69ds covered bya removable plate ll-0 which overlies the margin of the frame member as'clearly shown in Fig. 7. For fastening this plate 10, as well as the uppermost inner tread plate 44,s1otted pin and wedge fasteners shown generally at 1| maybe used as shown, these being probably more convenient than the long bolts 45 used'for the other removable plates.

The rear, vertical, and horizontal ends of the inner form -C are turned inwardly and downwardly to form an arched rear end 7 2, the arched margin of which is provided with a forwardly turned mounting lip 1-3. An angle iron might be welded to this margin in lieu of the lip -'i'3 if so desired. The front and rear ends of the inner extension form C are similarly formed with arched end members 14 and 15 having -opposit'ely turned marginal lips 16 and H. In connecting the main and extension molds A and A theend members '72 and J4 stand in spaced relation and the space therebetween is covered and enclosed by an arched yoke member 18 formed of flat strip material to overlap the margins and it to which it is secured by fasteners such as-24 or by wedged pins 19. When this space is then :filled initl'1e castingprocess, a reinforcing arch will be formed beneath the upper surface of the cast'structure.

A rear end cover is provided and may be placed at the rear of the extension .mold to which it is fastened by "inserting ear-s -8 at its upper end throughlccps '82 (see Fig. '6) formed on the upper rear angle iron t6. 'Thecover is cutaway to provide an arched inner margin which has a rearwardly turnedlipdiiiadapted to fall inalienment withthe lip ll to receive a yoke member Tel which is mounted by fasteners M or similar means. An archis thus formed also at the extreme rear of the structure, as will be understood.

When a platform :or extension :is not desired or required in the finished structure, the 'exten accuses sion mold A is set aside-and the rear cover 89 then is fastenedto the rear of the main mold A, in the same manner as that previously described, to form an arched rear wall as at I at the rear of the upper tread D.

An important feature resides in the insetting or depressing of all but the narrow upper and side margins of the cover 89 as shown at 85. This forms a panelled surface for the rear wall I and the narrow projecting edge L thus greatly facilitates installation of the steps as previously described.

Wherever mounting strips, angle irons and similar connecting means are used for connecting the parts, dowel pins or pilot pins shown generally at 86 are employed to properly guide and register the meeting face together while the fasteners are drawn tight.

In operation the mold A is assembled as shown and described with or without the extension mold, but with the various removable inner plates 44 and 19 laid aside. The mold is then inverted for filling as shown in Fig. 7, and is rested upon a support such as a table I22 carrying a frame I23 with vertical posts I24 of varying length to hold the mold level. Reinforcing rods (not shown) are then laid between the forms, if desired, and filling begins at the sides and exposed upper portions of the cavity between the forms. As the uppermost (in this position the lowermost) tread forming cavity becomes filled the plate 44 is put in place and the operation continues until all of the plates 44, including inner platform plate 10 if the extension mold is used, are in place and the mold is completely filled.

In this operation excess air and water may escape from the molds through vent holes 81 in the plates 44 and 10 and complete filling is thus insured without formation of air pockets in the structure. These vent holes further serve a useful purpose by first allowing the air and water to escape and then indicating as the cement itself begins to follow that the filling of the mold is complete.

With the mold thus filled it is allowed to stand until the mixture hardens, and then the removal operation takes place. For this operation the plates 44 and 19 are all removed and set aside after cleaning for the next casting operation. The inner form C (and C) with the plates removed is then lifted bodily from the cast structure and set aside, it being noted that all vertical surfaces are inclined or tapered to facilitate such lifting of the mold. The pins I are of course previously removed to free the cross bars 54.

The cast structure is then held in place in the outer form B (and B) by suitable temporary cross bars replacing the bars 54 or by other suitable means, and the mold is reverted to rest in normal upright position. The sides II (and 51), as well as cover 80, are then disconnected and pulled clear after which the outer riser and tread forming member I9 is lifted clear, leaving the completed cast structure free and ready for additional curing and aging.

For convenience in thus manipulating the mold a ball 88 from an overhead crane or lift (not shown) is pivotally connected at its lower ends to a bearing member 89 which may be adjusted forwardly or rearwardly in guide channels 99 on the mold sides to thus properly balance the mold as it is lifted, inverted, and reverted.

Inasmuch as the center members of the mold defining the steps and platform are separate from the sides of the mold, it becomes a simple matter to replace these members with others of any length to thus vary the overall width of the completed structure as may be desired. Likewise the mold may be initially formed and dimensioned to cast any desired number of steps as conditions may require. Furthermore, for lawn terrace use the sides F of the structure may not be desired and the outer form sides II are for this purpose parted along the line 9i (in Fig. 1) and provided with abutting detachably connected angle irons or fastening strips 92. The lower sections of the sides II may thus be removed and the sides of the casting finished off flush with the line 9| as the casting takes place to thus provide a step structure with only runners G at the sides, as will be readily apparent.

It is important in lifting the inner form C from the completed east structure that all sides be lifted evenly and equally, and for this purpose, as well as to aid in lifting this heavy form, I provide power lifts shown generally at 93. One lift is used at each corner'of the mold, and each comprises a bar 94 which is pivotally mounted by a bolt 95 to a corner of the inner form C with its outer end provided with a lifting screw 95 threaded through the bar to engage a corner of the outer form B. A handle or crank 97 on the upper end of the screw 96 is used for turning the screw toward the outer form and thus exerting a positive lifting force upon the inner form. The bar 94 is spaced from the inner form by a collar 98 so that the inner end may rest upon the adiacent cross bar 54 and thus counteract a tendency of the bar to rock upon the bolt 95 under strain. The cross bars 54 are braced by bars 93 at the proper points to resist pressure of the inner ends of the bars 94. The bars 94 may be swung aside (see Fig. 3) to expose the corner of the mold when filling the same.

The screws 96 are manipulated and turned each an equal amount to thus lift the inner form C evenly from the mold or, as shown in Fig. 4, they 7 may be simultaneously operated by a control mechanism I comprising shafts IIH running outwardly from a center point of the mold and rotated from a common crank I02 through beveled gears I93 and connected to each of the lift screws by beveled gears I04 in a well known manner. The extension mold A is similarly equipped with power lifts 93 and with a control mechanism if so desired.

The inner form C may be lifted partially from the mold and secured in that position by blocks (not shown) placed between the tie bars 54, and the outer form. This action has the effect of increasing the thickness of the molding cavity between the forms to thicken the treads D of the steps. Also, since the sides of the forms are inclined, as shown in Fig. 9, the side wall thickness of the structure will also be increased by this action and it is thus possible to provide either a heavy or light structure in the same form.

It is common practice to provide a step structure of this kind with an iron pipe railing, and for the purpose of providing sockets or seats for the upright parts of such a railing I provide the top members I2 and 58 of my mold with openings I05 in which are secured short necks I06. Removable plugs or plug molds I01 are then slidably fitted downwardly through these neck I06 and are retained in place by pins I98. The inner forms C and C' are provided below each opening I with downwardly extended housing members I09 entirely clearing the plug molds, and as the space thus formed is filled with the cementitious mixture it will be evident that clean and properly sized sockets H will be formed as desired. To remove the plug molds I01 the pins I08 are removed and a tool HI is inserted beneath a diametrical cross bar I I2 in the plugs to pry the same clear. Slots H3 allow this prying action to be carried out until the plug mold may be easily lifted clear.

A spring type clip fastener requiring no tools for installation or removal is shown in Fig. 8, and may be used if desired for fastening the various sections of the mold together. This fastener comprises a spring yoke H4, the ends of which are adapted normally to spring together and thus bring the pin end H5 of the yoke into registering openings H6 in the mold parts II! to be secured together. A shoulder H8 on the pin limits this action. The other end of the yoke is pivotally connected at H9 with a lever I20, an end of which engages one mold part II! and centers in the opening H6 therein. The parts are so shaped and proportioned that the lever I26 may be swung outwardly to release the fastener or swung inwardly to lock them, the spring tension of the yoke H4 being efiective to normally hold the lever in locking position as shown.

The operation of filling my improved mold involves the practice of a method of casting which is fully described and claimed in my copending application Serial No. 278,711, filed June 12, 1939, for Apparatus and method for precasting concrete stair structures. The cast structure thus formed has a nicely finished exposed surface and requires no touching up or supplementary finishing of any kind.

It is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims.

Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is: v

1. A mold for precasting concrete stair structures, comprising inner and outer mold forms, means supporting the forms in spaced relation for forming casting cavities therebetween, and

the said forms including inner and outer side forming members and inner and outer detachable center step forming portions bodily removable from the respective side forming members for replacement with others of different width to thereby cast steps of a preselected width.

2. A mold for casting concrete stair structures having a hollow underside portion, comprising a main mold and extension mold having inner and outer forms, and means on the molds for casting a reinforcing member beneath the structure intermediate its ends.

3. A mold for casting a concrete stair structure having a hollow underside, comprising a main mold having inner and outer forms, an extension mold also having inner and outer forms detachably connected to the said inner and outer forms of the main mold, and means at the junction of the molds for casting a transverse reinforcing arch on the hollow underside of the structure.

4. A mold for casting a concrete stair structure having steps and sides and a hollow underside, comprising inner and outer forms, means supporting the forms in spaced relation for easting said steps and sides, means at the upper and rear end of the form for closing the space between the forms and casting an arch member across the end of the structure, said means including a closure member formed to provide a narrow marginal projection around the top and outer sides of the said arch member.

5. A mold for precasting concrete stair structures, comprising inner and outer forms having portions adapted to mold corresponding inner and outer surfaces of the treads and risers for the stair, the said inner form having openings coinciding with inner surfaces of the treads, plates removably mounted over the openings, elongated bolts adapted to span the plates and having heads on one end and nuts on the other, and forks on the inner form adjacent the margins of the plates adapted to receive the heads and nuts of the bolts, the said forks being inclined whereby tightening of the nuts will urge the bolts against the plates and firmly seat the plates over the said openings.

FRANK KOGL. 

